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Chemical Consequences of Alkali Inhomogeneity in Cu 2 ZnSnS 4 Thin‐Film Solar Cells
Author(s) -
Gershon Talia,
Hamann Cayla,
Hopstaken Marinus,
Lee Yun Seog,
Shin Byungha,
Haight Richard
Publication year - 2015
Publication title -
advanced energy materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.08
H-Index - 220
eISSN - 1614-6840
pISSN - 1614-6832
DOI - 10.1002/aenm.201500922
Subject(s) - czts , materials science , diffusion , alkali metal , substrate (aquarium) , diffusion barrier , soda lime glass , thin film , kesterite , analytical chemistry (journal) , chemical physics , layer (electronics) , composite material , nanotechnology , thermodynamics , chemistry , physics , oceanography , organic chemistry , chromatography , geology
This study offers new insight into the role of Na in Cu 2 ZnSnS 4 (CZTS) thin film solar cells by studying samples with a spatially varying alkali distribution. This is achieved by omitting a diffusion barrier between the soda‐lime glass substrate and the Mo back contact, where compositional variations of the glass inherently result in non‐uniform alkali distributions in the CZTS. By correlating light beam induced current (LBIC) maps with secondary ion mass spectrometry composition maps, it is shown that samples containing regions of higher Na concentration (“hot spots”) have corresponding LBIC hot spots on comparable length scales. Samples containing an alkali diffusion barrier have lower LBIC dispersion; thus, LBIC can be used to evaluate non‐uniformity in CZTS devices, where a common cause is Na inhomogeneity. Moreover, it is shown that the Na hot spots are strongly correlated with other compositional variations in the device, including increased Cu in‐diffusion with the underlying MoS 2 layer and decreased diffusion of Cd to the back contact. Neither of these effects are well understood in CZTS devices, and neither have previously been correlated with the presence or absence of Na.